Process for the separation of fatty acid and rosin acid sodium salts and sterols from mixtures thereof



Feb.

ACID

19, 1946- J. J, LovAs Erm.

PROCESS FOR THE SEPARATION 0F FATTY ACID AND' ROSIN SODIUM SALTS ANDSTEROLS' FROM MIXTURES THEREOF Filed Aug. l, 1942 fre-.swam Wren/76.575m ATTOVET `Patented Feb. 19, 1946 PROCESS FOR THE SEPARATION OF FATTYACID AND ROSIN ACID SODIUM SALTS AND STEROLS FROlVI MIXTURES THEREOFJoseph `lohn Lovas, Ridgewood, and Paul F.

Bruins, Douglaston, N. Y.

Application August 1, 1942, Serial No. 453,288

13 Claims.

The present invention arises from the discovery by us that theconstituents of mixtures of fatty acid and rosin acid sodium salts canbe separated by the selective solvent action of certain ketone-watermixtures, such as acetone- Water mixtures and methyl ethyl ketone-Watermixtures; also that fatty acid soaps may be separated by the same meansfrom mixtures thereof with rosin soap and unsaponiable material,including sterols.

This application contains in part subject matter in our applicationfiled March 28, 1940, Serial No. 326,398. A practical and industriallyimportant application of this invention is in the separation andrecovery from crude kraft soap (or crude tall oil soap as it is alsocalled) of fatty and sodium salts, rosin acid sodium salts, andunsaponifiables including sterols,

While the process has general application, the same will be described inconnection with the treatment of crude kraft soap.

Crude kraft soap consists of various evaporated and salted-outcomponents of Waste black liquid obtained from the treatment ofconiferous wood by the soda-sulfate process, an example being Wetso ofWest Virginia Pulp 8a Paper Company, which has the following approximatecomposition:

. Percent Sodium salts of fatty acids 36.30 Sodium salts of rosin acids34.10 Unsaponiables 3.75 Sterols .85 Water 25.00

The rosin content may contain about 2% oxidized rosin.

In the drawing, Figure 1 represents a flow diagram of a Water-acetonesolution method for the separation of constituents of crude kraft soap.Figures 2 and 3 represent the solubility of various soaps in a ketone atconstant temperature.

EXAMPLE I said kraft soap acetone plus some water to make up thenecessary 97-3 mixture. The said mixture in the digestor is preferablysubjected to a temperature of about 50 C. or some other temperatureslightly below the boiling point of acetone for about 15 minutes. At theend of this period, a very substantial proportion of the sodium salts ofthe fatty acids separates out in the form of a precipitate, While theother substances go or remain in solution. If any oxidized rosin hasbeen present in the kraft soap, this too will separate out with thesodium salt of the fatty acid in the form of a precipitate.

While the precipitate may then be recovered, as by filtering, We preferthat the material be placed in a centrifuge 4 which separates the liquidcomponent from the precipitate, the former being conveyed to a cooler 5,the latter to a drier 7.

The liquid component, which is subjected to cooling contains in solutionsodium salt of rosin acid, sterols and other unsaponiables, as Well as asmall amount of sodium salt of fatty acids which has not precipitatedout. Upon cooling to about F. or by increasing the concentration ofacetone, a proportion of the second fraction of fatty acid sodium saltsprecipitates out together with a small amount of rosin acid sodiumsalts, the sterols and unsaponiables re-A maining vin solution by virtueof the acetone. These small quantities of mixed sodium salts arereturned to the digestor, or may be re-worked separately.

Now, with respect to the material in the drier 1, the same comprises thesodium salts of fatty acids and substantially all of the sodium salts ofoxidized rosin originally present in the Waste liquid. After drying, thelatter material is transferred to the hydrolyzer 8 to which is addedsulfuric acid by Way of pipe 9.

The effect of the sulfuric acid is to convert the sodium salts of thefatty acids to free fatty acids. After the hydrolyzving action or atSome convenient point in this reaction, some ligroin, hexane or othersuitable hydrocarbon is added to retain the oxidized rosin in solidcondition. In the hydrolizer, then, there are oxidized rosin protectedby the ligroin from going into solution, sodium sulfate, and free fattyacid. The oxidized rosin, ligroin and the free fatty acids aretransferred to a filter Il) where the oxidized rosin is separated fromthe ligroin and free fatty acid. The sodium sulfate from the hydrolyzeris drawn off.

After the separation of the oxidized rosin from the ligroin and freefatty acid, the latter two substances are transferred to a still Ilwhere the ligroin is distilled off and returned to the hydrolyzer 8 byway of pipe I3 while the free fatty acid is recovered through the pipeI2. The latter may contain a greater or less amount of rosin aciddepending upon the care with which the operation has been carried outand other factors.

At drying operation 1, traces of acetone are driven off by heat to thescrubber Il, and from there treated in the stripping column I5, fromwhence such acetone is returned to the digestor I by way of pipes I6, I1and I8.

Reverting to the liquid component derived from the filter 6: as stated,the latter comprises in dissolved condition sterols and otherunsaponifiables as well as sodium resinates. This material istransferred to the still I9 where the acetone and some water are drivenoff, leaving the material substantially free of acetone and deprived ofmore or less of its water content. The mass remaining after suchdistillation is placed in a separator 20 and there is added suiiicientligroin, hexane or the like, together with acetone, preferably insubstantially equal proportions, and sufiicient with the remainingwater, to form a homogeneous solution of the entire mixture. Water isthen added to cause separation into two layers, the top layer being ahydrocarbon solution of the pitch, sterols and other unsaponiables, andthe bottom layer being a water-lretone solution of sodium resinates. Thetwo layers are separated from each other by decantation or otherseparatory operation, the rosin acid soap layer being transferred tostill 2I where the acetone is distilled out and conveyed back to pipe 3.The water solution of rosin acid soap is delivered directly to ahydrolyzer 22 where sulfuric acid is added through pipe 23, and hexanethrough pipe 23a. This acid converts the sodium salt of rosin acid tothe free rosin acid and sodium sulfate. The mixture is allowed tosettle, forming two layers. The top layer, being a hexane solution ofrosin acids is then transferred to a still 24, where the hexane isdistilled off and returned to the separator 20, as indicated. There thenemanates from the still 24 free rosin acid which is removed.

Reverting now to the hexane pitch, sterols and unsaponifiables portionfrom the separator 20, the said material is transferred to a still 25where the hexane is driven oil and conveyed back to the separator 20 forre-use, the remaining pitch, sterols and unsaponiflables beingtransferred as a dark viscous mass to extractor 21 receiving hotacetone, preferably anhydrous. The hot acetone dissolves all smallamounts of sodium resinate which, although soluble in 97% acetonecontaining a small amount of water (3%) are insoluble in anhydrousacetone, so that when the material is transferred to filter 28, the

-insoluble substances will be separated from the hot acetone-solublepitch, sterols and unsaponifiables. The latter are placed incrystallizer 29 where, upon chilling of the acetone to a lowtemperature, preferably below 70 F., the sterols crystallize out. Thecrystallized sterols, remaining pitch, unsaponifiables and acetone areplaced in filter 30 where the crystallized sterols are separated fromthe dissolved pitch, unsaponiables and acetone. The latter material isplaced in a still 32 where the acetone is distilled oi and returned intocirculation while the unsaponiables, loosely called pitch remain behindand are removed from the still. The last-named mass of material can behydrolyzed and Otherwise treated to obtain certain desirable or usefulproducts, but this is no part of the present invention.

The sterols, ordinarily pure white in color, are

. sometimes contaminatedv with sodium salt of rosin acid or sodiumabietate; the latter may be removed as follows:

The mixture of sterols and sodium abietate is p dissolved in water toform an emulsion, and hydrolyzed with a slight excess of hydrochloricacid. The sterols and abietic acid are extracted by means of hot hexane,and then recovered from the hexane solution by distilling oil! thesolvent. The residue is then dissolved in anhydrous acetone, thesolution chilled to crystallize out the sterols, and filtered. Theacetone filtrate contains the abietic acid which can be recovered bydistilling oif the solvent.

As an illustration of the yields obtained by the above example of ourprocess of separation and recovery, in an actual operation, startingwith the composition- Per cent Sodium salts of fatty acids 36.30 Sodiumsalts of rosin acids 34.10 Unsaponifiables, and pitch 3.75 Sterols .85Water 25.00

some sodium saltof oxidized rosin acids.

tive index 1.484 30.2 Oxidized rosin acid .9 Free rosin avid 27.0Sterols (mainly in the form sitosterols) .81

Residual material 8.59

A preliminary separation of the oxidized rosin content of the startingmaterial may be effected by subjecting the latter to an acetone-watersolution in the proportion of '15% acetone and 25% Water, wherebysolution of the materials with the exception of the sodium salts ofoxidized rosin will be secured. The oxidized rosin being first removed,the solution may be passed to digestor 1 and acetone added to provide a97-3 acetone-water content. This, as has been shown, causes the sodiumsalts of the fatty acids to precipitate out. On the other hand, ifacetone is added so as to raise the acetone-water ratio to 99.5-.5,.both the fatty acid sodium salts and the rosin acid sodium saltsprecipitate out, leaving the unsaponiflables, including the pitch andsterols. in solution.

There are three main classifications into which the rosin acids may bedivided. Henceforth they shall be referred to as follows:

Type A-Hexane soluble abietic acid.

TypeB-Hexane insoluble rosin acid.

Type C-Rosin acid, the sodium salt of which is soluble in anhydrousacetone and hexane. This type has previously been referred to as pif/ch.

Exmrrn 1I Treat with anhydrous acetone 961.2 grams of spray dried soapwas Washed with three successive portion of 11/3 gallons of anhydrousacetone for each wash at a temperature of 50 C. The insoluble soap wasfiltered out and then dried until free of acetone. It was then dissolvedin hot water, and hydrolyzed by the addition of dilute sulfuric acid.

Hexane was then added to extract the resulting mixture of fatty androsin acids. The hexane solution was decanted, filtered, and then heatedto distill off the solvent. 672 grams (70.0% yield) of brown mixed acidswas obtained. On -analysis it was found to contain 57.2% fatty acid and42.8% abietic acid. 31 grams (3.2% yield) of light brown oxidized rosinwas filtered from the hexane solution of mixed acids.

'I'he acetone solution from which the fatty acid soaps had been filteredwas heated to distill off the acetone. The residue was dissolved inwater. Hexane was then added to extract the sterols and the sodium saltsof type C rosin acid, from the water solution of the sodium salts oftypes A and B rosin acid. The two layers formed on settling wereseparated. The top hexane layer was heated to distill oi the solvent.The residue was then dissolved in hot acetone. The solution was chilledand sterols were crystallized and filtered out. Additional sterols wererecovered by concentrating the filtrate and then crystallizing sterolsfrom it. Yield of sterols=18.25 grams=1.9%. The filtrate was heated todistill oi the acetone. A residue of 88.4 gm. (yield=9.2%) of type Csodium resinate was recovered.

The lower water layer from which the sterols and. type C sodium resinatewere extracted with hexane, was hydrolyzed by the addition of dilutesulfuric acid. Hexane was then added, to dissolve type A rosin acid,leaving the type B rosin acid undissolved. 'I'his type B rosi'n acid wasseparated from the hexane solution of type A rosin acid. The hexanesolution containing the type A rosin acid was decanted, and then heatedto distill off `the solvent, leaving a residue of type A-rosin acidweighing 17.3 gm. (yield=1.8%). The hexane insoluble rosin acid (type B)was recovered as a dark brown residue, Weighing 33.6 grams(yield-23.5%).

Summary of yields Per cent Mixed acids 70.0 Oxidized rosin 3.2 Type Arosin acid 1.8 Type B rosin acid 3.5 Type C sodium abietate 9.2 Sterols1.9

EXAMPLE III Treat with anhydrous acetone and then with 97% acetone 1000grams of spray dried soap was washed with three successive portions of1% gallons of anhydrous acetone for each wash at a temperature of 50 C.The insoluble soap was filtered out. The soap was then washed with sixsuccessive portions of 11/4 gallons of 97% acetone for each wash at 50C. The soap which remained insoluble consisted very largely of thesodium salts of the fatty acids. This soap was dissolved in water andhydrolyzed by the addition of dilute sulfuric acid. Hexane was thenadded to extract the resulting fatty acid. A considerable volume ofinsoluble, light weight, brown, oxidized rosin acid was precipitated. Itwas filtered out and dried. Yield of oxidized rosin=23 grams=2.3%. Thehexane solution of fatty acids was heated to distill off the solvent. Aresidue of 335 grams (yield=33.5%) of yellow fatty acids was obtained.On analysis it was found to contain 90.0% fatty acid and 10.0% rosinacid.

The 97% acetone solution of sodium resinates and sterols, 'from whichthe sodium salts of the fatty acids were filtered, was heated to distilloff the solvent. The residue, a dark brown paste, was dissolved in waterand hydrolyzed with dilute sulfuric acid. Hexane was added to extractthe resulting (type A) abietic acid. The hexane solution was heated todistill on the solvent. A residue of clear, brown rosin acid weighing286.0 grams was obtained (yleld=28.6%). On analysis it was found toconsist of 86.6% rosin acid and 13.4% fatty acid. 'I'he residue ofhexane insoluble rosin acid (type B) was a very dark brown material,weighing 33.0 grams (yield: 3.3%).

The original anhydrous acetone washings of the dried soap were heated todistill off the solvent. The residue was a mixture of the three types ofsodium resinate and sterols. The mixture was dissolved in water. Hexanewas then added to extract the sterols and type C-sodium resinate fromthe types A and B sodium resinate. The hexane solution was heated todistill oil. the solvent, leaving a residue of Sterols and type C sodiumresinate. I'he residue was dissolved in hot anhydrous acetone and thenchilled to crystallize the sterols. 'I'he Sterols were filtered out.Additional sterols were recovered by concentrating the acetone filtrateand then crystallizing sterols from it. Yield of sterols=l9.0 gm.=1.9%.The filtrate was heated to distill off the acetone. A residue of 92grams of type C sodium resinate was obtained (yield=9.2%) as a darkbrown residue.

The water solution from which the type C sodium resinate and sterols hadbeen extracted with hexane, was hydrolyzed with dilute sulfuric acid.

Hexane was then added to extract the type A rosin acid., The hexanesolution was decanted and then heated to distill oi the solvent. Aresidue of type A rosin acid, weighing 18.0 grams (yield=1.8%) wasobtained. The type B, hexane insoluble rosin acid was recovered as adark brown residue weighing 35 grams.

Summary of yields Per cent Fatty acids 33.5 Type A rosin acid 28.6Oxidized rosin 2.3 Type B rosin acid 6.8 Type A rosin acid 1.8 Sterols1.9 Type C sodium resinate 9.2

EXAMPLE IV Treat with methyl ethyl ketone 30 grams of spray dried soapwas dissolved in 300 cc. of a saturated solution of water in methylethyl ketone ketone) at room temperature.

0.30 gram of insoluble material (yield=1.0%) was ltered out. Theconcentration of ketone was `increased to 99% by the addition of 2250cc. of

The methyl ethyl ketone solution from which the fatty acid soaps hadbeen filtered was heated to distill olf the ketone., The residue wasdissolved in water with hexane to extract the sterols and type C sodiumresinate from the Water solution of the sodium soaps of types A and Brosin acid. The hexane solution was heated to distill off the solvent.The residue of Sterols and type C sodium resinate was dissolved in hotacetone. The solution was chilled, Sterols were crystallized and thenfiltered out. 'Additional sterols were recovered by concentrating theacetone ltrate and then recrystallizing sterols from it. Yield ofstero1s=0.45 gram=1.52%. The filtrate was heated to distill olf theacetone. A residue weighing 1.66 grams=5.52% of type C sodium rcsinatewas recovered.

The water solution of the sodium soaps of types A and B rosin acids washydrolyzed with dilute sulfuric acid. Hexane was added to extract thetype A rosin acid. The hexane solution was decanted and then heated todistill olf the solvent. A residue of clear, light brown abietic acid,type A, was obtained, weighing 6.4 grams (yield=2l.35%). The hexaneinsolute type B rosin acid was recovered as a dark brown residueweighing 6.6 grams (yield=22.0%).

Summary of yields Any aliphatic ketones in which water is soluble, or,at least slightly soluble, may be employed in our process. In theexamples, acetone and methylethyl ketone were specified, but in general,ketones with a structure containing up to 8 or 9 carbon atoms may beused and, as examples, we may mention di-ethyl ketone and ethyl propylketone. Water is generally insoluble in the higher ketones.

From the above it will be seen that a method has been provided wherebyfrom crude kraft soap, constituting a low grade source and either withits normal water content or dried, free fatty acids, free rosin acidsand sterols may be severally separated and recovered; that the foregoingmethod, at an intermediate stage, enables the recovery of the fatty acidsodium salts from the rosin acid sodium salt components and sterols, onefrom the other, to be used or further processed, and. that the method,Within certain limits, is capable of being varied to meet variations ofthe starting product and the nature of the recovery desired.

The above described process may be employed with advantage in connectionwith compositions or mixtures of fatty acid sodium salts, rosin andsodium salts, pitch and sterols and other unsaponiiiables obtained fromsources other than waste black liquor of the soda-sulfate process.

By the use of varying ratios of acetone-water mixtures between anhydrousand 97% acetone, an insoluble product may be obtained, varying from 55%to 95% fatty acid sodium salts and 4% to 45% rosin acid sodium salts.

Again, it should be borne in mind, that the type of higher fatty acidsodium salt may vary with the characteristics of the starting material.In wood pulp cook liquor, which is given merely as one example, thesodium fatty acid salt is comprised chiefly of the sodium salts of thefatty acids; oleic, linoleic, linolinic, ricinoleic, and possibly,depending on the specific source of the liquor, may even contain suchfatty acids as stearic, palmitic and hydroxystearic.

Having described ourinvention, what we claim and desire to secure byLetters Patent is as follows:

1. The process of separating the constituents of kraft pulp mill soapwhich comprises extracting the same with a mixture of about 97%aliphatic ketone of not more than 9 carbon atoms per molecule and 3%water whereby the sodium salts of fatty acids and oxidized rosin acidsare separated out as insoluble precipitate.

2. Process in accordance with claim 1 wherein the insoluble precipitateis removed; the ketone is removed from the remaining solution; thenadding to the remaining solution water and a hydrocarbon selected fromthe group consisting of khexane and ligroin to dissolve the sodiumresinates contained therein and thereby forming an aqueous andnon-aqueous layers; and separating said layers.

3. Process in accordance with claim 1 wherein the insoluble precipitateis removed; the ketone is removed therefrom, and the residue ishydrolyzed with a mineral acid in the presence of water; then to saidhydrolysate there is added a hydrocarbon selected from the groupconsisting of hexane and ligroin thereby forming an aqueous layer, and ahydrocarbon layer containing dissolved fatty acid and suspended oxidizedrosins acids; removing the hydrocarbon layer and filtering the same toremove the oxidized rosin acids; removing the hydrocarbon from thefiltrate by distilling the same to recover the fatty acids.

4. The process of separating and recovering the acid constituents ofcrude kraft soap which comprises subjecting the same to the selectivesolvent action of a mixture of about 97% acetone and 3% Water, wherebysodium salts of fatty acids are separated out, separating the latterfrom the solution portion, subjecting the sodium salts of fatty acids tohydrolysis to obtain the free fatty acids.

5. The process in accordance with claim 4, wherein there is added to thehydrolyzer for solid portion water and a low boiling point hydrocarbonselected from the group consisting of hexane and ligroin in which theSterols, pitch and other unsaponifiables are soluble in which the freefatty acids are soluble and in which the oxidized rosin is insoluble.

6. The process of separating sodium salts of fatty acids, sodium saltsof rosin acid, pitch and unsaponii'iable matter from a mixture thereof,which comprises subjecting said mixture to the selective action of aketone-water mixture the ketone being an aliphatic ketone of not morethan 9 carbon atoms per molecule and in which water may be at leastpartially soluble, the proportion of water being to about 3% to separateout a major proportion of the said sodium salts of fatty acids whilemaintaining the remaining substances in solution, and removing theundissolved material.

'7. The process of separating sodium salts of fatty acids and sodiumsalts of rosin acid from a mixture thereof, which comprises subjectingthe mixture to the action of a lower-aliphatic ketone- 'water mixture,the aliphatic ketone being of not more than 9 carbon atoms per` moleculein which water may be at least partially soluble, the proportion ofWater in said solvent mixture being about 3% to maintain substantiallyinsoluble the sodium salts of fatty acids, and removing the latter.

8. The process of separating the constituents of crude kraft soap toremove the sodium salts of oxidized rosin acids therefrom, whichcomprises extracting the crude kraft soap with a mixture of about 75%acetone and 25% water.

9. The process of treating crude kraft soap containing sodium salts ofoxidized rosin acid which comprises `iirst treating the crude kraft soapwith a mixture of about 75% acetone and 25% water, to dissolve al1 ofthe components of said soap with the exception of said salts of oxidizedrosin acids, separating the latter from the solution portion, adding tothe latter suicient a acetone to increase the percentage of acetone inthe acetonewater mixture to 97-3, whereby sodium salts of fatty acidsare precipitated out, and removing the latter.

10. The process of separating sodium salts of fatty acids from sodiumsalts of rosin acids in mixtures thereof, which comprises dissolving thelatter with a mixture of about 97% acetone and 3% water to effectseparation of said component soaps, and separating the same.

11. The process of separating sodium salts of fatty acids and sodiumsalts of rosin acids from a mixture thereof with .pitch andunsaponiables, which comprises dissolving the pitch and unsaponifiablesthereof with an acetone-Water mix- 30 ture where the acetone is inexcess of 97% so as to precipitate out the component soaps.

12. The process of separating sterols, pitch and other unsaponifiablesfrom a mixture thereof, with sodium salts of rosin acids which comprisesadding thereto acetone and water and a low boiling hydrocarbon selectedfrom the group consisting lof hexane and ligroin in which the sterols,

pitch and other unsaponiables are soluble so as to form 'two layers, inthe water layer of which are the sodium salts of rosin acids and in thehydrocarbon layer of which are the pitch, sterols,

and other unsaponiables, separating said layers, f

distilling the hydrocarbon layer to remove the latter and leave thepitch, sterols and other unsaponifiables, treating the latter with hotacetone, thence chilling the resulting solution to crystallize outsterols, and removing the crystalline material.

13. The process of separating the constituents of substantially drykraft pulp mill soap which comprises extracting the same by the solventaction of an aliphatic ketonic solvent of not more than 9 carbon atomsper molecule, and not less than 97% ketone concentration, and in whichwater-may be at least partially soluble, whereby the unsaponiablefraction is dissolved and the sodium soaps are precipitated.

JOSEPH JOHN LOVAS. PAUL F. BRUINS.

